This invention relates to novel catalysts and their use in polyolefin production, in particular to cyclic-carbene-xcex7-ligand catalysts useful in the preparation of polyolefins, in particular polymers of C2-8 olefins, more especially polypropylenes and most especially polyethenes.
Polyolefins of superior mechanical and processing properties may be obtained if the molecular-weight distribution is tailored to the end use of the polymer. Traditional olefin polymerization catalysts, such as chromium on silica, produce polyethylenes with a wide molecular weight distribution. Such materials are well suited for making moulded products. However, these moulded products would be significantly improved if it were possible to produce a polymer containing a tailored molecular weight distribution combined with controlled insertion of comonomer into the desired part of the molecular weight distribution.
One solution to this problem is to produce the olefin polymer using two or more metallocene complex catalysts simultaneously. Typically, combinations of zirconocene complexes have been disclosed. However, while zirconocene dichloride is useful to produce the low molecular weight fraction of a polymer, no satisfactory comonomer control is achieved, ie. branched polyolefin chains are produced in the presence of a mixed olefin feedstock (for example ethylene-hexene) This is generally true for the overwhelming majority of the known metallocene complexes.
It is therefore desirable to identify an olefin polymerization catalyst exhibiting comonomer control, ie. which will not build certain comonomers into the growing polymer chain even though such comonomers are present in the polymerisation feedstock.
It is an object of the invention to provide such a catalyst system.
Thus viewed from one aspect the invention provides a process for the catalysed polymerization of a an olefin, especially a C2-8 xcex1-olefin, preferably a C2 or C3 xcex1-olefin, more preferably ethene, characterised in that as a catalyst or catalyst precursor is used a cyclic carbene-xcex7-ligand complex comprising a catalytically effective coordinated metal, preferably a group 6 metal, and more especially chromium.
Viewed from a further aspect the invention provides an olefin polymerization catalyst or catalyst precursor comprising a cyclic carbene-xcex7-ligand complex comprising a catalytically effective coordinated metal, preferably a group 6 metal, and more especially chromium.
In the cyclic carbene-xcex7-ligand complex, the cyclic carbene ligand may be any cyclic carbene capable of coordinating to the metal. Typically the carbene is heterocyclic with the C: providing one ring atom, and especially preferably with the ring unsaturated. In general, the atoms adjacent the C: will be substituted, preferably with bulky substituents containing up to 30 non-hydrogen atoms, preferably at least 4 non-hydrogens e.g. containing 4 to 12 carbon atoms. Moreover the substituent itself may comprise a further carbene structure. More preferably, the carbene comprises a 5 membered, preferably mono-unsaturated, heterocyclic ring which contains 2, 3 or 4 ring nitrogens, two of which are optionally substituted and 1, 2 or 3 ring carbons one of which (the C: atom) is adjacent at least one ring nitrogen and is unsubstituted with any remaining ring carbon optionally being substituted. Thus for example the carbene may be of formula Ia or Ib 
where each X may independently represent N or an optionally substituted CH group; and each R1 is hydrogen, or an optionally substituted organic group.
Carbenes of formula Ia, especially where the R1 groups are bulky substituents and more especially where the ring atoms of each X are carbon, are particularly preferred.
The carbenes of formula Ia or Ib are sometimes referred to as Arduengo carbenes (as opposed to the Fischer and Schrock carbenes which are more commonly encountered in publications relating to organometallic complexes). The Arduengo carbenes tend to be more stablexe2x80x94if they dissociate from a metal complex they usually have sufficiently large half lives to re-enter the metal""s coordination sphere. Such stability facilitates the synthesis of substituted derivatives allowing greater freedom to modify the electronic and steric properties of the carbene. The Arduengo carbenes moreover tend to bind efficiently to metals whether in low or high oxidation states as opposed to Fischer and Schrock carbenes which favour low and high oxidation states respectively; this is advantageous in polymerization catalysis where oxidation state changes may occur. The Arduengo carbenes are efficient 2-electron donor ligands (comparable to P(CH3)3 or P(C6H11)3) with no tendency to act as Π acceptorsxe2x80x94again in contrast to Fischer and Schrock carbenesxe2x80x94and may be used in place of phosphine ligands.
The strong metal:Arduengo carbene bond strengths (comparable to or greater than metal:phosphine bond strengths) mean that the complexes are thermally robust. Accordingly such carbenes have good catalyst lifetimes and thermal stabilities.
Many such carbenes of formulae Ia or Ib are already known as ligands, e.g. compounds having the following skeletal structures (ie. omitting ring substituents): 
(where n is from 1 to 6).
The range of substituents the carbene ring nitrogens and ring carbons may carry is very large, with different substitution patterns resulting in variations in the properties of the resulting catalyst.
Thus for example substituents may be selected from halogen atoms, non-carbon oxyacid groups and derivatives thereof, and optionally substituted alkyl, aralkyl and aryl groups, e.g. such groups substituted by groups selected from alkyl, aryl, amino, hydroxy, alkoxy, oxo, oxa, carboxy, thia, sulphur oxyacid and halo groups and combinations thereof. Examples of particular ring substituents include for example methyl, ethyl, i-propyl, t-butyl, n-butyl, n-hexyl, cyclohexyl, phenyl, hydroxyphenyl, optionally substituted ferrocenyl (e.g. (C5H4)Fe(C5H5)), benzyl, methylbenzyl, l-phenyl-ethyl, mesityl, methylnaphthyl, ethoxyethyl, diphenylmethyl, ethylaminoethyl, diethylamino-methyl, 2-(diethylamino)-ethyl, 2-carboxy-ethyl, 2-sulphoxy-ethyl, 4-sulphoxy-butyl, 2-ethoxycarbonyl-ethyl, chlorophenyl, adamantyl, dihydroimidazol-ylidinylmethyl, dihydropyrazolylidinylmethyl, 2,6-diisopropylphenyl, or dihydrotriazolylidinylmethyl groups.
Particular examples of suitable carbenes include compounds of formulae IIa to IIj 
wherein n is from 1 to 6 and each R1, which is the same or different, preferably the same, represents a C1-6 alkyl group, a C4-10 mono or polycyclic cycloalkyl group, a C4-10 cycloalkyl-C1-4 alkyl group, an aryl group, an aryl-C1-4 alkyl group, a C1-6 alkyl-aryl-C1-4 alkyl group, a carboxy group or derivative thereof (e.g. an ester group), or a ferrocenyl group, in which any alkyl, alkylene, aryl or arylene moiety is optionally substituted, e.g. with amino, hydroxy, alkoxy, halo, nitro, cyano, oxyacid (e.g. carbon oxyacid or sulphur oxyacid) or oxyacid derivative (thus by way of example R1 might represent 2-hydroxy-phenyl); and R2 which may be the same or different is hydrogen, halogen, C1-6 alkyl or an aryl group or two R2 groups on adjacent carbons can together form an optionally substituted carbocyclic group, e.g. a 5 to 7 membered ring.
Unless otherwise specified, alkyl groups or alkylene moieties referred to herein may conveniently contain 1 to 10, more preferably 1 to 6 carbons and are linear or branched. Likewise unless otherwise specified aryl groups are preferably homo or heterocyclic containing 5 to 7 ring atoms per ring and with such rings containing 0, 1, 2, 3 or 4 ring heteroatoms selected from 0, N and S, preferably 0, 1, 2 or 3 N atoms, and with the groups containing a total of 5 to 16 ring atoms. The ring atoms may be substituted, e.g. by alkyl groups and other groups listed above or by fused saturated or unsaturated rings. Examples of typical aryl groups include phenyl, naphthyl, mesityl, 2,6-diisopropyl-phenyl, 2,6-ditertbutyl-phenyl, and 2,6-ditertbutyl-4-methylphenyl.
Examples of suitable carbenenes and carbene-metal complexes and procedures for their synthesis are described in the literature, e.g. in xc3x6fele, K. J. Organomet. Chem., 1968,12, 42-43; Wanzlick, H. W. et al., Angew. Chem., Int. Ed. Engl. 1968, 7, 141-142; xc3x6fele, K. et al., Angew. Chem., Int. Ed. Engl. 1970, 9,739-740; Schxc3x6nherr, H. J. et al., Chem. Ber. 1970, 103, 1037-1046; Schxc3x6nherr, H. J. et al., Liebigs Ann. Chem. 1970, 731, 176-179; Luger, P. et al., Acta Cryst., Sect. B 1971, B27, 2276-2279; xc3x6fele K. et al., Chem. Ber. 1972, 105, 529-540; xc3x6fele, K. et al., Z. Naturforsch. 1973, 28B, 306-309; Kreiter, C. G. et al., Chem. Ber. 1976, 109, 1749-1758; xc3x6fele, K. et al., Z. Naturforsch. 1976, 31B, 1070-1077; Krist, H. G. Dissertation, Technische Universitxc3xa4t Mxc3xcnchen, 1986; Bonati, F. et al., J. Organomet. Chem. 1989, 375, 147-160; Arduengo, A. J., III et al., J Am. Chem. Soc. 1991, 113, 361-363; Bonati, F. et al., J Organomet. Chem. 1991, 408, 271-280; Arduengo, A. J., III et al., J Am. Chem. Soc. 1992, 114, 5530-5534; Herrmann, W. A. et al., Chem. Ber. 1992, 125, 1795-1799; Britten, I. F. et al., Acta Cryst., Sect. C 1992, C48, 1600-1603; Mihailos, D. Dissertation, Technische Universitxc3xa4t Mxc3xcnchen, 1992; Arduengo, A. I., III et al., Organometallics 1993, 12, 3405-3409; Arduengo, A. I. et al., J Organomet. Chem. 1993, 462, 13-18; xc3x96fele, K. et al., J Organomet. Chem. 1993, 459, 177-184; Kuhn, N. et al., Synthesis 1993, 561-562; Arduengo, A. I., III et al., J Am. Chem. Soc. 1994, 116, 4391-4394; Arduengo, A. I., III. et al., J Am. Chem. Soc. 1994, 116, 7927-7928; Schumann, H. et al., Angew. Chem., Int. Ed. Engl. 1994, 33, 1733-1734; Kuhn, N. et al., J Organomet. Chem. 1994, 470, C8-C11; Herrmann, W. A. et al., J Organomet. Chem. 1994, 480, C7-C9; Schumann, H. et al., Chem. Ber. 1994, 127, 2369-2372; Dias, H. V. R. et al., Tetrahedron Lett. 1994, 35, 1365-1366; Gridnev, A. A., et al., Synth. Commun. 1994, 24, 1547-1555; Herrmann, W. A., Organometallics 1995, 14, 1085-1086; Herrmann, W. A. et al., Angew. Chem., Int. Ed. Engl. 1995, 34, 2371-2374; xc3x96fele, K. et al., J Organomet. Chem. 1995, 498, 1-14; Herrmann, W. A. et al., J Organomet. Chem. 1995, 501, C1-C4; Kuhn, N. et al., Inorg. Chim. Acta 1995, 238, 179-181; Herrmann, W. A. et al., Chem. Eur. J 1996, 2, 772-780; Herrmann, W. A. et al., Chem. Eur. J 1996, 2, 1627-1636; Herrmann, W. A. et al., Angew. Chem., Int. Ed. Engl. 1996, 35, 2805-2807; Herrmann, W. A. et al., J Organomet. Chem. 1996, 520, 231-234; Herrmann, W. A. et al., Organometallics, 1997, 16, 682-688; Herrmann, W. A. et al., Organometallics 1997, 16, 2209-2212; Herrmann, W. A. et al., Organometallics 1997, 16, 2472-2477; Herrmann, W. A. et al., Angew. Chem., Int. Ed. Engl. 1997, 36, 1049-1067; Herrmann, W. A. et al., J Organomet. Chem. 1997, 530, 259-262; Kocher, C. et al., J Organomet. Chem. 1997, 532, 261-265; Arduengo et al., J. Am. Chem. Soc., 119: 12742 (1997); Hermann et al., Angew. Chem. Int. Ed. Engl., 36, 2162 (1997); Kxc3x6cher et al., J. Organomet. Chem., 532: 26 (1997); Gardiner et al., J. Organomet. Chem., 572: 239 (1999); J. Organomet. Chem., 572: 177 (1999); Herrmann et al., J. Organomet. Chem., 547: 357 (1997); Wang et al., Organometallics 17: 972 (1998); Liu et al., Organometallics 17: 993 (1998); Herrmann et al., Organometallics 17: 2162 (1998); Weskamp et al., Angew. Chem. Int. Ed. Engl. 37: 2490 (1998); Green et al., J. Organomet. Chem. 554: 175 (1998); Herrmann et al., J. Organomet. Chem. 557: 93 (1998); Arduengo et al., Chemie Unserer Zeit 32: 6 (1998); Voges et al., Organometallics 18: 529 (1999); Abernethy et al., J. Am. Chem. Soc. 121: 2329 (1999); Huang et al., J. Am. Chem. Soc. 121: 2624 (1999);.Wang et al., Organometallics 18: 1216 (1999); McGuinness et al., Organometallics 18: 1596 (1999); WO97/34875 (Hoechst); EP-A-719753 (Hoechst); EP-A-719758 (Hoechst); DE-A-4447066 (Hoechst); and DE-A-4447070 (Hoechst).
Other suitable carbenes may be synthesised analogously.
Besides the unsaturated carbene ligands, ring saturated carbenes may also be used. Examples are described for example by Denk et al., in Angew. Chem. Int. Ed. Engl., 36: 2607 (1997) and by Sellmann et al., in J. Organomet. Chem., 541: 291 (1997).
Particularly suitable carbenes include: 1,3-dimethyl-imidazoline-2-ylidene, 1,3-di-i-propyl-imidazoline-2-ylidene, 1,3-di-n-butyl-imidazoline-2-ylidene, 1,3-di-t-butyl-imidazoline-2-ylidene, 1,3-di-trimethylsilyl-imidazoline-2-ylidene, 1,3-di-benzyl-imidazoline-2-ylidene, 1,3-di-cyclohexyl-imidazoline-2-ylidene, 1,3-di-phenyl-imidazoline-2-ylidene, 1,3-bis(2,6-di-isopropyl)phenyl-imidazoline-2-ylidene, 1,3-bis(2,6-di-tertbutyl)phenyl-imidazoline-2-ylidene, 1,3-di-(1-naphthyl)-imidazoline-2-ylidene, 1,3-di-(anthracyl)-imidazoline-2-ylidene, 1-methyl-3-i-propyl-imidazoline-2-ylidene, 1-n-butyl-3-i-propyl-imidazoline-2-ylidene, 1-t-butyl-3-i-propyl-imidazoline-2-ylidene, 1-trimethylsilyl-3-i-propyl-imidazoline-2-ylidene, 1-benzyl-3-i-propyl-imidazoline-2-ylidene, 1-cyclohexyl-3-i-propyl-imidazoline-2-ylidene, 1-phenyl-3-i-propyl-imidazoline-2-ylidene, 1-bis(2,6-diisopropyl-phenyl)3-i-propyl-imidazoline-2-ylidene, 1-bis(2,6-ditertbutyl-phenyl)-3-i-propyl-imidazoline-2-ylidene, 1-mesityl-3-i-propyl-imidazoline-2-ylidene, 1-(1-naphthyl)-3-i-propyl-imidazoline-2-ylidene, 1-(1-anthracyl)-3-i-propyl-imidazoline-2-ylidene, 1-methyl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-i-propyl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-n-butyl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-t-butyl-3-bis(2,6-diisopropyl-phenyl) -imidazoline-2-ylidene, 1-trimethylsilyl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-benzyl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-cyclohexyl-3-bis(2,6-diisopropyl-phenyl) -imidazoline-2-ylidene, 1-phenyl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-bis (2, 6-ditertbutyl-phenyl)-3-bis (2, 6-diisopropyl) -phenyl)-imidazoline-2-ylidene, 1-mesityl-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-(1-naphthyl)-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-(1-anthracyl)-3-bis(2,6-diisopropyl-phenyl)-imidazoline-2-ylidene, 1-methyl-3-mesityl-imidazoline-2-ylidene, 1-i-propyl-3-mesityl-imidazoline-2-ylidene, 1-n-butyl-3-mesityl-imidazoline-2-ylidene, 1-t-butyl-3-mesityl-imidazoline-2-ylidene, 1-trimethylsilyl-3-mesityl-imidazoline-2-ylidene, 1-benzyl-3-mesityl-imidazoline-2-ylidene, 1-cyclohexyl-3-mesityl-imidazoline-2-ylidene, i-phenyl-3-mesityl-imidazoline-2-ylidene, 1-bis(2,6-diisopropyl-phenyl)-3-mesityl-imidazoline-2-ylidene, 1-bis(2,6-ditertbutyl-phenyl)-3-mesityl-imidazoline-2-ylidene, 1- (1-naphthyl)-3-mesityl-imidazoline-2-ylidene and 1-(1-anthracyl)-3-mesityl-imidazoline-2-ylidene.
The xcex7-bonding ligand in the carbene-xcex7-ligand complex used according to the invention may be any convenient mono or polycyclic ligand capable of xcex7-bonding the catalytically effective metal using their xcex7-orbitals, e.g. to form so-called xe2x80x9csandwichxe2x80x9d or half sandwich complexes. xcex7-bonding can thus be distinguished over bonding where only one atom of the ligand is bound to the metal, e.g. so-called sigma bonding. Typically the xcex7-bonding ligand is a cyclopentadienyl ligand in which one or more of the ring carbons are optionally substituted, e.g. with halogen atoms or alkyl, aryl or aralkyl groups, or with fused rings, e.g. fused benzene or cyclohexene rings. Thus the xcex7-ligand may be any of the xcex7-ligands conventionally used in or proposed for metallocene catalysts. Moreover, if desired, the xcex7-bonding ring may be coupled via a bridging group or directly to the carbene moiety.
Thus the cyclic carbene and xcex7-ligand may conveniently comprise the following skeletal structure 
where Z is a bond or a one to three atom bridge, e.g. a bridge comprising carbon and/or silicon atoms. Such a bridge may conveniently be xe2x80x94CH2xe2x80x94, CH2CH2 or Si(CH3)2. The ring atoms of this skeletal structure may conveniently be substituted, for example by pendant or fused ring substituents. Such substitution is desirably analogous to that described herein for the non-bridged cyclic carbene and xcex7-ligands.
Bridged cyclic carbine/xcex7-ligand ligands may be prepared by conjugating cyclic carbenes and xcex7-ligands (or precursors therefor), preferably using difunctional bridging agents, e.g. alkylating or analogous agents (see Herrmann et al., J. Organomet. Chem. 547: 357 (1997)). By way of example the following schemes may be used to produce xe2x80x94CH2xe2x80x94 and xe2x80x94CH2CH2xe2x80x94 bridged materials: 
Bridged cyclic carbene/xcex7-ligand liganded metals are preferably selected from groups 4 to 6 metals, especially Ti, Zr, Hf and Cr.
The xcex7-bonding ligand may for example be of formula III
CpYmxe2x80x83xe2x80x83(III)
where Cp is an unsubstituted, mono-substituted or polysubstituted homo or heterocyclic cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, benzindenyl, cyclopenta[l]phenanthrenyl, azulenyl, or octahydrofluorenyl ligand; m is zero or an integer having a value of 1, 2, 3, 4 or 5; and where present each Y which may be the same or different is a substituent attached to the cyclopentadienyl ring moiety of Cp and selected from halogen atoms, and alkyl, alkenyl, aryl, aralkyl, alkoxy, alkylthio, alkylamino, (alkyl)2P, alkylsilyloxy, alkylgermyloxy, acyl and acyloxy groups or one Y comprises an atom or group providing an atom chain comprising 1 to 4 atoms selected from C, O, S, N, Si and P, especially C and Si (e.g. an ethylene group) to a second unsubstituted, mono-substituted or polysubstituted homo or heterocyclic cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl or octahydrofluorenyl ligand group.
In the xcex7-bonding ligands of formula III, the non cyclopentadienyl rings may themselves be optionally substituted e.g. by halogen atoms or groups containing 1 to 10 carbon atoms.
Many examples of each xcex7-bonding ligands and their synthesis are known from the literature, see for example: Mxc3x6hring et al. J. Organomet. Chem 479:1-29 (1994), Brintzinger et al. Angew. Chem. Int. Ed. Engl. 34:1143-1170 (1995).
Examples of suitable xcex7-bonding ligands include the following:
cyclopentadienyl, indenyl, fluorenyl, pentamethyl-cyclopentadienyl, methyl-cyclopentadienyl, 1,3-di-methyl-cyclopentadienyl, i-propyl-cyclopentadienyl, 1,3-di-i-propyl-cyclopentadienyl, n-butyl-cyclopentadienyl, 1,3-di-n-butyl-cyclopentadienyl, t-butyl-cyclopentadienyl, 1,3-di-t-butyl-cyclopentadienyl, trimethylsilyl-cyclopentadienyl, 1,3-di-trimethylsilyl-cyclopentadienyl, benzyl-cyclopentadienyl, 1,3-di-benzyl-cyclopentadienyl, phenyl-cyclopentadienyl, 1,3-di-phenyl -cyclopentadienyl, naphthyl-cyclopentadienyl, 1,3-di-naphthyl-cyclopentadienyl, 1-methyl-indenyl. 1,3,4-tri-methyl-cyclopentadienyl, 1-i-propyl-indenyl. 1,3,4-tri-i-propyl-cyclopentadienyl, 1-n-butyl-indenyl, 1,3,4-tri-n-butyl-cyclopentadienyl, 1-t-butyl-indenyl, 1,3,4-tri-t-butyl-cyclopentadienyl, 1-trimethylsilyl-indenyl, 1,3,4-tri-trimethylsilyl-cyclopentadienyl, 1-benzyl-indenyl, 1,3,4-tri-benzyl-cyclopentadienyl, 1-phenyl-indenyl, 1,3,4-tri-phenyl-cyclopentadienyl, 1-naphthyl-indenyl, 1,3,4-tri-naphthyl-cyclopentadienyl, 1,4-di-methyl-indenyl, 1,4-di-i-propyl-indenyl, 1,4-di-n-butyl-indenyl, 1,4-di-t-butyl-indenyl, 1,4-di-trimethylsilyl-indenyl, 1,4-di-benzyl-indenyl, 1,4-di-phenyl-indenyl, 1,4-di-naphthyl-indenyl, methyl-fluorenyl, i-propyl-fluorenyl, n-butyl-fluorenyl, t-butyl-fluorenyl, trimethylsilyl-fluorenyl, benzyl-fluorenyl, phenyl-fluorenyl, naphthyl-fluorenyl, 5,8-di-methyl-fluorenyl, 5,8-di-i-propyl-fluorenyl, 5,8-di-n-butyl-fluorenyl, 5,8-di-t-butyl-fluorenyl, 5,8-di-trimethylsilyl-fluorenyl, 5,8-di-benzyl-fluorenyl, 5,8-di-phenyl-fluorenyl and 5,8-di-naphthyl-fluorenyl.
Besides the carbene and xcex7-bonding ligands, the carbene-xcex7-ligand complex used according to the invention may include other ligands; typically these may be halide, hydride, alkyl, aryl, alkoxy, aryloxy, amide, carbamide or other two electron donor groups.
The carbene-xcex7-ligand complexes used according to the invention may be produced relatively straight-forwardly by reacting a cyclopentadienyl-metal complex with a carbene or by reacting a metallocene with a salt, e.g. an imidazolium salt, of a protonated carbene. Sigma-bonded hydrocarbyl groups may subsequently be introduced for example by reaction with Grignard reagents. Such processes form further aspects of the present invention.
For use in olefin polymerization, the carbene-xcex7-ligand complexes of the invention may be used together with a co-catalyst (or catalyst activator).
Thus viewed from a further aspect the invention provides an olefin polymerization catalyst system comprising (a) a cyclic carbene-xcex7-ligand complex according to the invention and (b) a co-catalyst.
As a co-catalyst, an aluminoxane is preferred. Preferred aluminoxanes include C1-10 alkyl aluminoxanes, in particular methyl aluminoxane (MAO). Such aluminoxanes may be used as the sole co-catalyst or alternatively may be used together with other co-catalysts. Thus besides or in addition to aluminoxanes other cation complex forming catalyst activators may be used. In this regard mention may be made of the silver and boron compounds known in the art. What is required of such activators is that they should react with the carbene-xcex7-ligand complex to yield an organometallic cation and a non-coordinating anion (see for example the discussion on non-coordinating anions J in EP-A-617052 (Asahi)).
Aluminoxane co-catalysts are described by Hoechst in WO 94/28034. These are linear or cyclic oligomers having up to 40, preferably 3 to 20, "Brketopenst"Al(Rxe2x80x3)O"Brketclosest" repeat units (where Rxe2x80x3 is hydrogen, C1-10 alkyl (preferably methyl) or C6-18 aryl or mixtures thereof).
In the polymerization process of the invention, more than one olefin monomers may be used. It is preferred that the comonomers be used in a minor amount, e.g. 0.5 to 40%, preferably 1 to 6% by weight, relative to the total monomer weight with the major monomer (e.g. ethene) making up the major amount, e.g. 60 to 99.5% by weight. Such comonomers may be other C2-8 xcex1-olefins but may also be more bulky monomers containing unsaturated carbon carbon bonds (especially Cxe2x95x90C bonds) and, for example, up to 20 carbons, preferably up to 16 carbons, more preferably up to 14 carbons. Such comonomers may thus be mono or polycyclic, fused ring or unfused compounds containing one or more, e.g. 1, 2 or 3, unsaturated carbon carbon bonds. Examples of suitable such bulky comonomers include norbornene, norbornadiene and dicyclopentadiene. The use of the carbene-xcex7-ligand catalysts of the invention is thus important in enabling the incorporation of such bulky comonomers within polyolefin products. Thus viewed from a further aspect the invention comprises a copolymer of a C2-8 xcex1-olefin and a mono or polycyclic monoene or polyene.
Viewed from a yet further aspect the invention provides a process for the catalysed polymerization of olefins, characterised in that as a catalyst is used a catalyst system according to the invention.
Viewed from a further aspect the invention provides a polymer article (e.g. a fibre, film or moulded article) formed from a polymer composition comprising a polymer produced by a process according to the invention, said composition optionally containing further components, e.g. further polymers, fillers, antioxidants, coloring agents, stabilizers (e.g. UV stabilizers), etc.
Polymerization according to the invention may be performed using standard polymerization techniques, e.g. gas phase, slurry phase or liquid phase polymerization and using conventional polymerization reactors, e.g. loop reactors, gas phase reactors, or stirred tank reactors, or combinations thereof.
Polymerization according to the invention may, as with conventional polymerizations, be effected in the presence of a solvent, e.g. an alkane (for example a C3-7 alkane such as propane or n-butane), an aromatic compound (e.g. toluene) or a cycloaliphatic (e.g. cyclohexane).
The polymerization according to the invention is conveniently carried out in the temperature range of 0-300xc2x0 C., more preferred from 60-120xc2x0 C. Partial pressure range employed for the olefin(s) is conveniently from 1-2000 bars, more preferably from 5-20 bars.
It is particularly desirable that the carbene-xcex7-ligand complex be supported on a solid substrate for use in such polymerization reactions. Such substrates are preferably porous particulates, e.g. inorganic oxides such as silica, alumina, silica-alumina or zirconia, inorganic halides such as magnesium chloride, or porous polymer particles, e.g. acrylate polymer particles or styrene-divinylbenzene polymer particles which optionally carry functional groups such as hydroxy, carboxyl etc. Particle sizes are preferably in the range 20 to 60 xcexcm and porosities are preferably in the range 1 to 3 mL/mg. The complex may be loaded onto the support before or more preferably after it has been reacted with a co-catalyst. Desirably inorganic supports are heat treated (calcined) before being loaded with the complex.
While the catalytic metal in the carbene-xcex7-ligand complexes used according to the invention is preferably a group 6 metal (e.g. Cr, Mo or W) and especially chromium, other catalytically effective transition or lanthanide metals can be used. Thus examples of the metal which may be coordinated in the carbene metallocene complex include group 3, 4, 5, 6, 7, 8, 9 and 10 metals, lanthanides and actinides. Particular metals which may be mentioned include Ti, Cr, Zr, Hf, V, Mn, Sc, Y, Nb, Ta, Re, Fe, Co, Ru, Os, Rh, Ir, Ni, Pd, Pt, Sm, Eu, La, Yb and Er.
The invention will now be described further with reference to the following non-limiting Examples.
All manipulations involving organometallic compounds were carried out with use of vacuum line, Schlenk, syringe, or drybox techniques. Dichioromethane, dichloromethane-d2, chioroform-d were distilled from CaH2. THF was distilled from sodium benzophenone ketyl. 1H NMR spectra were recorded on Bruker DPX 200 and 300 instruments. Chemical shifts are reported in ppm relative to tetramethylsilane, with the residual solvent proton resonance as internal standards. Melting points were measured in capillary tubes sealed under vacuum. Solid state magnetic susceptibility study of CpCrCl (1,3-dimesitylimidazoline-2-ylidene) was conducted on a Quantum Design MPMS with a 5.5 Tesla super-conducting magnet and a SQUID detection system. Solution magnetic moments were measured by a modification of the Evan""s method (C6D5H as a reference) (see J. Chem. Soc. 2003-2005 (1959), J. Mag. Res. (1989) 169-173, and J. Chem. Educ. (1995) 39-40). EPR spectra were taken on a Bruker 200D-SRC instrument.
Polymerisations with ethylene were carried out either at atmospheric pressure in glass reactors or at 38 bar in a 1 litre autoclave. The polymerisations at atmospheric pressure were performed at 30xc2x0 C. in toluene solution, while the high pressure polymerisations were carried out at 70 to 90xc2x0 C. in isobutane slurry. In both reactors the pressure was maintained constant by continuously adding ethylene. In examples where either hydrogen, 1-hexene or norbornene was added, these were added prior to the polymerisation. Melt index (MI) and high load melt index (HLMI) were measured according to ASTM standard D1238 condition A and F respectively. Total methyl content was measured by infrared spectroscopy according to ASTM standard D2238-68, while the vinyl and transvinylene contents were determined as described by R. Blom et al. in J. Mol. Catal., 91 (1994) 237.
X-ray crystallography: Crystals were obtained by cooling a toluene/pentane solution at xe2x88x9235xc2x0 C. A crystal (e.g. of dimensions 0.60xc3x970.55xc3x970.40 mm) was mounted on a glass fiber using paratone oil. X-ray data was collected on a Siemens SMART CCD diffractometer (Siemens Analytical X-ray Instruments Inc., Madison, Wis., USA) using graphite monochromated MoKxcex1 radiation. Data collection method: xcfx89-scan, range 0.6xc2x0, crystal to detector distance 5 cm. Data reduction and cell determination were carried out with the SAINT and XPREP programs (Siemens Analytical X-ray Instruments Inc., Madison, Wis., USA). Absorption corrections were applied by the use of the SADABS program (Siemens Analytical X-ray Instruments Inc., Madison, Wis., USA). The structure was determined and refined using the SHELXTL program package (Siemens Analytical X-ray Instruments Inc., Madison, Wis., USA). The non-hydrogen atoms were refined with anisotropic thermal parameters; hydrogen positions were calculated from geometrical criteria and given isotropic thermal parameters.
Cp=cyclopentadienyl
Ph=phenyl
Cp*=pentamethylcyclopentadienyl
The publications referred to herein are hereby incorporated by reference.